Wheel structure

Abstract

A large-diameter part, the diameter of which is larger than the diameter in the center, is provided at the edges of a rim via parts having a difference in a level. Curled parts are provided on both edges of the rim by curling the large-diameter part. Each end face of the curled parts is touched to the parts having a difference in a level. The rigidity of the side of the edge of the rim can be enhanced by providing the parts having a difference in a level to the rim. As a result, the rigidity of the whole wheel can be enhanced and in addition, as a disc and the rim are not required to be thickened, the weight of the wheel can be prevented from being increased.

What is claimed is:  
     
       1. A wheel structure comprising: 
       a rim including a central portion, an inner portion and an outer portion;  
       an inner curled portion formed on a terminal end of said inner portion; and  
       an outer curled portion formed on a terminal end of said outer portion;  
       said central portion being of a first predetermined diameter;  
       said inner portion being of a second predetermined diameter;  
       said outer portion being of a third predetermined diameter;  
       wherein said second predetermined diameter of said inner portion is greater in diameter relative to said third predetermined diameter of said outer portion.  
     
     
       2. The wheel structure according to  claim 1 , wherein a protrusion for reinforcement is formed within said outer curled portion, said protrusion for reinforcement protruding inside the outer curled portion of said outer portion. 
     
     
       3. The wheel structure according to  claim 1 , wherein a protrusion for reinforcement is formed within said inner curled portion, said protrusion for reinforcement protruding inside the inner curled portion of said inner portion. 
     
     
       4. The wheel structure according to  claim 1 , wherein said outer curled portion includes a larger-diameter part, a curled part and a straight part for touching the outer portion for forming the outer curled portion. 
     
     
       5. The wheel structure according to  claim 1 , wherein said inner curled portion includes a larger-diameter part, a curled part and a straight part for touching the inner portion for forming the inner curled portion. 
     
     
       6. The wheel structure according to  claim 4 , wherein a protrusion for reinforcement protrudes from the large-diameter part of said outer curled portion and said protrusion being formed inside the curled part of said outer portion. 
     
     
       7. The wheel structure according to  claim 5 , wherein a protrusion for reinforcement protrudes from the large-diameter part of said inner curled portion and said protrusion being formed inside the curled part of said inner portion. 
     
     
       8. The wheel structure according to  claim 1 , and further including a opening formed in said outer curled portion for providing drainage for water. 
     
     
       9. A wheel structure comprising: 
       an inner wheel including a central portion and an inner portion, said inner portion being of a first predetermined diameter;  
       an inner curled portion being formed on an inner surface of said inner wheel;  
       an outer wheel including a central portion and an outer portion, said outer portion being of a second predetermined diameter; and  
       an outer curled portion being formed on an exterior surface of said outer wheel;  
       wherein said first predetermined diameter of said inner portion is greater in diameter relative to the second predetermined diameter of said outer portion.  
     
     
       10. The wheel structure according to  claim 9 , wherein a protrusion for reinforcement is formed within said outer curled portion, said protrusion for reinforcement protruding inside the outer curled portion of said outer portion. 
     
     
       11. The wheel structure according to  claim 9 , wherein a protrusion for reinforcement is formed within said inner curled portion, said protrusion for reinforcement protruding inside the inner curled portion of said inner portion. 
     
     
       12. The wheel structure according to  claim 9 , wherein said outer curled portion includes a larger-diameter part, a curled part and a straight part for touching the outer portion for forming the outer curled portion. 
     
     
       13. The wheel structure according to  claim 9 , wherein said inner curled portion includes a larger-diameter part, a curled part and a straight part for touching the inner portion for forming the inner curled portion. 
     
     
       14. The wheel structure according to  claim 12 , wherein a protrusion for reinforcement protrudes from the large-diameter part of said outer curled portion and said protrusion being formed inside the curled part of said outer portion. 
     
     
       15. The wheel structure according to  claim 13 , wherein a protrusion for reinforcement protrudes from the large-diameter part of said inner curled portion and said protrusion being formed inside the curled part of said inner portion. 
     
     
       16. The wheel structure according to  claim 9 , and further including a opening formed in said outer curled portion for providing drainage for water. 
     
     
       17. The wheel structure according to  claim 9 , wherein said inner wheel is jointed to said outer wheel for forming said wheel structure. 
     
     
       18. The wheel structure according to  claim 17 , and further including a central plate for mounting said inner wheel relative to said outer wheel for forming said wheel structure.